[Adsix]

hello everyone, i bought a M235i with catless downpipe, intercooler, charge pipe, tune and possibly more back in in January 2024 with 78k miles now 90k and it was in mint condition beside for an OFHG leak nothing besides that, a few months ago i had the OFHG leak and coolant hose leak fixed and with that came 6 trips back and forth to the terrible dealership that worked on it. was getting low oil pressure codes due to a aftermarket oil filter that was used. was sorted out after the 7th trip of them "fixing it" fast forward no more than a month later no codes besides for one night where i got a drivetrain malfunction along with the codes

121002 Charging pressure sensor, electrical: Short circuit to earth. Intermittent

120408 Charging pressure control: switch-off as consequence. intermittent

121202 Charging pressure sensor, plausibility, after-run: pressure too low. intermittent

- symptoms before any CEL or codes would pop up

The car would feel like it WANTED stall when coming to a stop like it would get quiet when stopping, when taking off after a cold start 1st or 2nd gear a huge jerk while on throttle even 5% as if the car died this would happen twice. When rolling downhill in 1st gear the exhaust sounded like it was choking like gurgling but not the normal bmw tune type of gurgle. when warm starting the car after an hour or two letting it sit. it would have trouble starting. it would start first try but would choke up and want to die for 20 seconds till rpms evened out almost like a e85 cold start in negative degree weather. thats all i can really remember this would happen a month or two before the codes would pop up. and reverse felt really clunky with the rpms, slight throttle would jump and drop as if the car wanted to die but drive felt somewhat normal.

-symptoms now with codes.

essentially all the same as before but now when idling rpms will act weird car gets louder as if rpms rise go down go sideways everything, sometimes the rpm gauge on the cluster moves with the sounds others it doesnt. sometimes limp mode engages others it doesn't typically drives like terrible. for a week it drove normal, i think? been having car trouble (same problem on and off) today for the 4th time i picked up the car for THIS problem and either it was in my head but it felt weird coldstarts dont have the same kick that they used too. and overall driving felt a bit slugish maybe. did a few pulls and power felt okay. then idled for about 30 min and when i took off malfunction popped up at 20% throttle. engine got loud turbos wouldnt spool, rpms acted weird not as severely as before. got home restarted the car and codes went away drove it back to the shop for the 5th time now all in all cars been in the shop a total of 12-14 times in 2 months changed the hose from the intake to the purge valve to the charge pipe, boost pressure sensor i think. and some pigtail for some wire. dont know what to do now. pleae help.

[pbonsalb]

I would find an independent shop familiar with modded 235s. The dealer, as you have learned, is expensive. Posting in a 235 forum would at least put you in touch with some other 235 modders who might have experienced similar problems.

[BMWbiker]

Originally Posted by Adsix

hello everyone, i bought a M235i with catless downpipe, intercooler, charge pipe, tune and possibly more back in in January 2024 with 78k miles now 90k and it was in mint condition beside for an OFHG leak nothing besides that, a few months ago i had the OFHG leak and coolant hose leak fixed and with that came 6 trips back and forth to the terrible dealership that worked on it. was getting low oil pressure codes due to a aftermarket oil filter that was used. was sorted out after the 7th trip of them "fixing it" fast forward no more than a month later no codes besides for one night where i got a drivetrain malfunction along with the codes

121002 Charging pressure sensor, electrical: Short circuit to earth. Intermittent

120408 Charging pressure control: switch-off as consequence. intermittent

121202 Charging pressure sensor, plausibility, after-run: pressure too low. intermittent

- symptoms before any CEL or codes would pop up

The car would feel like it WANTED stall when coming to a stop like it would get quiet when stopping, when taking off after a cold start 1st or 2nd gear a huge jerk while on throttle even 5% as if the car died this would happen twice. When rolling downhill in 1st gear the exhaust sounded like it was choking like gurgling but not the normal bmw tune type of gurgle. when warm starting the car after an hour or two letting it sit. it would have trouble starting. it would start first try but would choke up and want to die for 20 seconds till rpms evened out almost like a e85 cold start in negative degree weather. thats all i can [...]

My local dealer has a strict rule of not working on cars with significant non-BMW parts, unless they are going to be removed and replaced with OEM BMW parts. The conversation I had with them had to do with cars that had been repaired with non-OEM parts because insurance companies cheaped out. I never asked, but I assume that it also applies to cars like yours.

Best wishes for getting it all sorted out.

[DrVenture]

Beside the sound advice of finding a shop with a top notch diagnostician, I would suggest the following: All the codes that you posted have to do with the charging pressure sensor. I would suspect one of three things:

1. Faulty charge pressure sensor
2. An issue with the wiring/connectors to the charge pressure sensor (121002 Charging pressure sensor, electrical: Short circuit to earth. Intermittent).
3. Something affecting the charge pressure, like a leak (121202 pressure too low).

Since the car was worked on extensively, I would be very suspicious that a wire to the charge sensor is pinched or a connector is not plugged in securely. I would check that circuit using schematics to identify the wiring and connectors. And test/swap the charge pressure sensor. If no problem found, I would look for a leak from the turbos (charge pipe crack/damage?). Perhaps even a problem with the waste gate solenoid not functioning properly.